Researchers at the University of Vermont are hoping to give nature a hand in fighting a deadly parasite devastating moose populations in Vermont.The winter tick, also knows as the moose tick, is a relentless predator whose strength is in numbers. Tens of thousands of them can attach to a single animal, bleeding them into an anemic, weakened state. A study in the Canadian Journal of Zoology reports these parasites are responsible for a 70% death rate among moose calves in northern New England over a three-year period, a rate the journal calls "unprecedented."
But there may be some good news for moose. VPR's Mitch Wertlieb spoke with Cheryl Sullivan, a Ph.D student at UVM's Entomology Research Lab, about using a naturally occurring fungus to kill ticks.
Sullivan described how so many winter ticks can become attached to even a single moose.
"What happens with this tick is the adults, the fed female mated adults, will feed on the moose in the spring and they'll drop off to the forest floor," she said. "And historically, they used to fall on snow and ice, which would kill them, so they wouldn't be able to lay eggs. So when they fall, if there's no snowpack, the females are able to get under the leaf litter and lay thousands and thousands of eggs."
Sullivan said the eggs then hatch in the summertime.
"And they'll have this cluster of larvae that sit at the forest floor until day-length triggers them to quest in the fall. ... When these ticks quest, they ascend the vegetation in thousands," she said. "And so you have these tick bombs all across the landscape. So when moose come in contact with these tick bombs, they just get thousands and thousands of ticks on them at one time."
The fungus that Sullivan is studying is called Metarhizium anisopliae. It is deadly to ticks and could theoretically be introduced to soil to intercept the ticks in their larval stage.
"What happens is the spore will attach to the outer layer of the tick," Sullivan said. "So then it sits there, it's like: 'Oh, this is great! I've got my target acquired!' So then it germinates and it colonizes the inside of the tick. Once it grows inside, it rips apart the organs. So then, it emerges from the host under the right temperature and humidity and produces spores, which are then dispersed into the environment to infect other target arthropods."
Sullivan said that one of the advantages of the fungus is that it appears to have very little effect on arthropods other than the ticks that it targets. Even so, she said it is not a "silver bullet," and that the fungus needs to be used as part of an "integrated pest management program."
"We're not talking about treating the entire range of moose habitat," she said. "We're seeking to identify localized areas where moose tend to be at higher densities, some place like a clear cut where there's optimal habitat."
